Conventional antennas used on portable two-way radio equipment typically are operated as a whip or helix type antenna and are designed to resonate at one or more desired wavelength. Antennas of this type are generally designed to operate at a 50 ohm input impedance. As is well known, these types of antennas generally extend out from the radio housing which significantly increases the perceived size of the radio housing.
It should be recognized that at a given center frequency, a significant reduction in the height of the conventional antenna will greatly decrease the antenna input impedance from a 50 ohm nominal value. This mismatch ultimately will cause a higher reflected power to the radio's power amplifier and a loss of the radio's transmitter power efficiency. Although circuitry can be used to match a lower antenna impedance to a 50 ohm nominal value, this circuitry can be complex, introducing significant insertion loss while ultimately adding additional manufacturing time and expense.
Thus, the need exists for a space efficient antenna structure that can be easily used within a radio housing having a 50 ohms impedance at resonant frequency in view of its limited size.